Don't waste a lot of time trying to find the correct band combination to hold your phone exactly over the eyepiece opening. If the band tension is not just right, or with too many bands, too tight or too loose, the phone camera will not stay over the opening above the eyepiece and won't have the ability to undergo fine positioning adjustments.
The photos show how to position one band (front and back connections) and allow the side positioned camera to reach the opening and maintain its position. One band was removed because two bands put too much tension on the phone and trying to position it resulted in the wrong position.
Left: the backside of the Acuter stock phone mount should look like this for positioning the camera with the proper tension. The use of only one band is needed.
The reason for this unusual design is there are no phone side grippers. I tried several different phone mounts with side grippers and they all interfered with the side buttons on the phone and could not be used.
This applies to the Apple iPhone 6 Plus and Xs Max.
The designers at Acuter Optics knew what they were doing when they designed this mobile phone holder. It does not pinch the sides of the phone and does not interfere with the side buttons or the operation of the iPhone. Read about bad phone mounts:
https://otisastro.blogspot.com/2022/05/bad-phone-camera-mounts.html
